Unions in Nevada have poured money and occasional vitriol into a battle between three pro-union candidates. One union has even joined a lawsuit against the state Democratic Party.

It wasn't supposed to be this way. In moving Nevada's caucus to the front of the primary calendar, national Democratic leaders were offering unions an opportunity to influence the nomination. In exchange, the thriving labor movement here would get a head start mobilizing its rank and file for the November general election in this swing state.

But the 21st-century face of US organized labor – particularly the service industries that have flourished in high-growth areas like Vegas – is showing itself to be more independent and risk-taking with its political deals, say experts.

"This is totally unlike the old labor political activity," says Richard Hurd, professor of industrial and labor relations at Cornell University in Ithaca, N.Y. "These unions have broken away from the AFL-CIO and they are trying to forge a new path. Their decision to endorse Obama, who never had any major union endorsements until they came along – that's the kind of thing they want to do: something path-breaking."

Traditionally, labor unions' approach is to nurture relationships with longtime, mainstream politicians, says Dr. Hurd. The SEIU and the Culinary Workers Union, by contrast, are "far more aggressive," he says.

"In reaching their decision, they undoubtedly took into account what sort of access they might gain if they make an endorsement that pans out," says Hurd. "If they are the first big unions to make an endorsement, then they are right there."

But Obama's few endorsements bring with them the most workers. The culinary union's 60,000 members top the combined local membership of Senator Clinton's or Mr. Edwards's endorsements.

To some extent, the division of union members diminishes any one candidate's labor advantage, says Peter Francia, a political scientist at East Carolina University in Greenville, N.C. "The fact that they split three ways suggests that the winner will probably owe their victory to which union is better able to get their people to the polls, and potentially to other groups that are part of that candidate's coalition."

The competition to deliver, plus the extraordinarily tight race, has seen one pro-Clinton union launch anti-Obama ads in Iowa and New Hampshire. In Nevada, the money is flowing in to pay for new ads and ground operations.

Meanwhile, local media reported how a state assemblyman toured a Hispanic neighborhood with Clinton in an effort to get Hispanic culinary workers to break ranks for her. Whether union workers would be comfortable doing that in the public forum of a caucus is unclear.

Then there's the lawsuit.

The state's teachers union, the Nevada State Education Association (NSEA), joined a lawsuit against the state Democratic Party and its plan to hold caucuses at some casinos on the Strip. These special "at-large" precincts would let shift workers downtown take part without going home. Half of all casino workers on the Strip belong to the culinary union. Without this accommodation, the union leadership says, thousands of its workers would be disenfranchised.

The teachers union argues, however, that their members need a special accommodation, too. Schools will be used as caucus sites, requiring janitors and other union members to staff precincts that may not be their own.

"NSEA's only interest was fairness, not disenfranchising anyone," says executive director Terry Hickman. His board has not endorsed a candidate, he says, and he discounts the notion that high-level staff ties to Clinton could influence it.

The culinary union wasn't amused. Its chief has accused the teachers union of being "used" by the Clinton campaign.

The suit asking for the at-large precincts to be disallowed came two days after the union endorsed Obama.

The Clintons deny they are behind the lawsuit but don't denounce it. At press time, a ruling was imminent.